The present invention is directed to a novel air-to-air type heat exchange device adaptable for attachment to an exhaust stack of either an oil or natural gas furnace assembly. Heat is extracted from the hot exhaust gases passing through the heat exchange device to provide an additional source of heating for residential as well as commercial buildings.
While it is known to attach a heat exchanger to an exhaust gas passageway, the known devices have proved both cumbersome and costly, while failing to efficiently transfer heat from the exhaust gases to the ambient air passageway.
As for example, in U.S. Pat. No. 3,533,466, issued Oct. 13, 1970, to Saloman et al., a heat exchanger is attached to the exhaust gas passage of a refuse incinerator to cool the exhaust gases emanating therefrom. A complex multi-fan assembly continuously directs a variable volume of cooling air past the exhaust gas passageway. A thermostat is positioned within an outlet of the exhaust gas passageway and selectively actuates one of the fans responsive to an increase in the temperature of the exhaust gas.
The multi-fan arrangement disclosed in Saloman et al. requires a separate motor and control mechanism for each fan which proves to be both cumbersome and costly. Applicant, in comparison, provides a unitary device requiring a single fan motor and associated control mechanism.
The thermostat in Saloman et al. is positioned within the outlet of the hot exhaust gases and is susceptible to accidental off-cycling due to the large temperature variations which may often occur within a furnace exhaust.
In response to this problem, applicant has designed a novel assembly wherein the thermostat is positioned within the ambient air passageway which is much less susceptible to large temperature variations. Furthermore, applicant's thermostat is less likely to prematurely fail because it does not come in direct contact with the hot exhaust gases.
While the U.S. Pat. No. 3,884,292 issued May 20, 1975, to Pessolano et al. does disclose a heat exchange device including a thermostat positioned in the ambient air passageway, the Pessolano et al. device can be distinguished as requiring a plurality of sealed intermediate heat transfer tubes which are neither described nor required by applicant's device.
As will be discussed in detail, the present invention provides a heat exchange device that overcomes the problems existing in prior art devices while including a plurality of novel design features for maximizing the heat transfer efficiency.